From 08d0ce30e0e4fcb5f06c90fe40387b1ce9324833 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Mon, 10 Jul 2023 18:35:46 +0000 Subject: riscv: Implement syscall wrappers Commit f0bddf50586d ("riscv: entry: Convert to generic entry") moved syscall handling to C code, which exposed function pointer type mismatches that trip fine-grained forward-edge Control-Flow Integrity (CFI) checks as syscall handlers are all called through the same syscall_t pointer type. To fix the type mismatches, implement pt_regs based syscall wrappers similarly to x86 and arm64. This patch is based on arm64 syscall wrappers added in commit 4378a7d4be30 ("arm64: implement syscall wrappers"), where the main goal was to minimize the risk of userspace-controlled values being used under speculation. This may be a concern for riscv in future as well. Following other architectures, the syscall wrappers generate three functions for each syscall; __riscv_sys_ takes a pt_regs pointer and extracts arguments from registers, __se_sys_ is a sign-extension wrapper that casts the long arguments to the correct types for the real syscall implementation, which is named __do_sys_. Reviewed-by: Kees Cook Tested-by: Nathan Chancellor Signed-off-by: Sami Tolvanen Link: https://lore.kernel.org/r/20230710183544.999540-9-samitolvanen@google.com Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/compat_syscall_table.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'arch/riscv/kernel/compat_syscall_table.c') diff --git a/arch/riscv/kernel/compat_syscall_table.c b/arch/riscv/kernel/compat_syscall_table.c index 651f2b009c28..ad7f2d712f5f 100644 --- a/arch/riscv/kernel/compat_syscall_table.c +++ b/arch/riscv/kernel/compat_syscall_table.c @@ -9,11 +9,15 @@ #include #undef __SYSCALL -#define __SYSCALL(nr, call) [nr] = (call), +#define __SYSCALL(nr, call) asmlinkage long __riscv_##call(const struct pt_regs *); +#include + +#undef __SYSCALL +#define __SYSCALL(nr, call) [nr] = __riscv_##call, asmlinkage long compat_sys_rt_sigreturn(void); void * const compat_sys_call_table[__NR_syscalls] = { - [0 ... __NR_syscalls - 1] = sys_ni_syscall, + [0 ... __NR_syscalls - 1] = __riscv_sys_ni_syscall, #include }; -- cgit